Muffle, muffle furnace, and the like



Aug. 20, 1929.

P. H. P. MONCKTON MUFFLE MUFFLE FURNACE, AND THE LIKE Filed Nov. 23,1927 8 23 U h K a 242 V 8 Mil/3 226 V 7 1o 27 4 [z 45 30 20 n n 55 34- zI o g gO fzN OflMM g i 52 I 516 as 5 QM 8 7 Patented Aug. 20, 1929.

UNITED STATES PATENT OFFICE.

PHILIP HENRY PARR MONCKTON, OF JOHANNESBURG, TRANSVAAL, SOUTH AFRICA,ASSIGNOR TO WILLIAM HENRY CROSS, OF JOHANNESBURG, UNION OF SOUTH AFRICA.

MUFFLE, MUFFLE FURNACE, AND THE LIKE.

Application filed November 23, 1927, Serial No. 235,230, and in theUnion of South Africa September 16, 1927.

This invention relates to muflles, mufile furnaces and the like, whichare heated electrically.

Electrically heated muffles generally have not proved satisfactoryinvuse as, owing to the fact that the elements have had to be renewedfrequently owing to their having been quickly burnt out or destroyed,such mufl'les have not been economical in use.

Now one object of the invention is to design and construct anelectrically heated muffle or the like in such a way that the heatingelements will not be subject to such premature destruction. Further obects of the invention are to ensure better control of the heat, byvarying or regulating the electric current, and better control of thesupply of air, by means of induced draught.

Amongst the advantages obtained in a muffie constructed according to theinvention, as compared with existing mufiles, are, that it is moreefiicient in use, that it occupies less space, that it is more, quicklyheated and the heat more effectively distributed in the muflie orheating chamber and, furthermore, that the atmosphere in the vicinity ofthe muflle is cooler, as the loss of heat by radiation is comparativelysmall.

In the accompanying sheet of drawings I illustrate a practicalembodiment of my invention, wherein Fig. 1 shows a half-sectionalelevat1on of the complete muflle.

Fig. 2 is a central sectional side elevat1on of the complete muffle.

Fig. 3 is a plan view of the electrical heating element or resistance,removed from the heating chamber, and

Fig. 4 is a sectional elevat1on lllustratlng a modified form of themufile chamber.

In the embodiment of the invention illustrated in the annexed drawings,the muflie or furnace includes an inner part or box 1, the interior ofwhich constitutes the heating chamber of the muffle,-on the floor ofwhich the cupels are placed, and an outer casing or enclosing structure.The part or box 1 is open at the front, as seen in Fig. 2, and partiallyclosed at the back or rear end. It may be constructed of fireclay orother suitable refractory material and is shown provided with a falsebottom 2 in the form of a slab, which may be made of asbestos cement orother suitable material. The mufile chamber is shown provided along bothsides with a row of holes 3 which allow of the passage into the heatingchamber 4 of preheated air.

The outer casing or enclosing structure may, as shown, include anexternal metal casing 5 which is open at the backsee Fig. 2-and formedat the top, bottom and sides of the front with a flange 6. Inside theeasing 5, at the sides, top and bottom, are arranged slabs 7 of asbestoscement. Inside the slabs 7 is arranged a box, lining or part 8,constructed of fireclay or other suitable refractory material. This boxor part 8, like the box or part 1, is open at the front and partiallyclosed at the back. The box or lining 8 of the outer casing is somewhatlarger internally than the external dimensions of the part or box 1providing the heating chamber, so that a space 9 is left or providedbetween the fireclay lining or box 8 and said box or part 1 at the topand at both sides. The part or box 1 is arranged inside the lining 8 ofthe outer casing on the bottom thereof and is placed against the back ofsaid lining 8.

The outer casing at the front has secured to it a plate 10, in which isformed an opening 10 and which may be made of cement asbestos and isshown fixed by screws 11 to the flanges 6.

In the front end of the box or part 8, at the back of the plate 10, istightly fitted a slab or piece 12 which contacts with the front end ofthe box or part 1 and so closes the space 9 at the front of the furnace.The slab 12 is provided with an opening 13 which opens into the heatingchamber 4: and is closed by the door 14. The false bottom 2 is shownslightly longer than the bottom of the box or part 1, so that the slab12 fits under the forwardly projecting portion of the false bottom 2beyond the front end of the part or box 1. Through the slab 12 holes 15are formed which allow heated air to pass from the front end of thespace 9 to the open front end of the heating chamber 1. The front plate10 is shown provided with guides 16 for the door 14, and the door 14 isshown consisting of a metal casing 17 lined with a block of refractorymaterial 18. In the door let an inspection hole or opening 19 isprovided which is adapted to be closed by a hinged door or cover 20. Thedoor 14 is counterbalanced by a weight 21 which is at tached to the doorby a cord or flexible connection 22, which passes over the guide pulleys23 carried by brackets 24 fixed to the top of the casing 5 at the front,14- being a stop for limiting the upward movement of the door let.

At the front of the opening in the front plate 10, which opening 10 isclosed by the sliding door 14, a rest or plate 25 is provided, carriedby a bracket 26, for use in putting the cuples into and taking them outof the heating chamber.

A hole or opening 27 is provided, which passes through the outermetallic casing 5, the slab 7, and the top of the box or lining 8, andleads into the space 9, which allows of the passage of induced air tosaid space 9. Such induced air is heated in its passage through thespace 9 from'the inlet 27 'to the rows of holes 3 in the sides of'thebox or part 1 and to the holes 15 provided in the slab or piece 12 atthe front of the heating chamber 4.

An opening 28 is provided through the back of the box or part 1, theback of the box or lining 8 and through a slab or sheet 28 which isfitted into the back of the outer casing against the back of the box orlining 8. This opening 28 forms the outlet for thefumes and gases fromthe heating chamber 4. Inthe opening 28 in the back of the box or lining8 and in the slab or sheet 28 is fitted and cemented a tubular fireclaypiece or socket 29 which communic ates with a vertical pipe or flue 30through a coupling piece or nipple 31 and a T piece 32. In the pipe orflue 30 means are provided for introducing a jet of compressed air rthelike for inducing the passage of air through the muffle. The'meansfor effecting this are shown consisting of the upwardly directed nozzle33 attached to an air supply pipe 34 in which is provideda valve 35. Inthe bottom of the T piece a screw plug or cover 36 is provided forremoving any accumulated litharge or other deposit from the T piece 32or flue 30. The jet of compressed air ensures the passage of the inducedair current through the furnace and may also be used for blowing out ofthe flue or pipe 30 any accumulated fumes. The T piece 32 is showncarried or supported by 'legs or supports 37.

v The electrical heating means for the muflle includes an element orresistance which is arranged in the upper portion of the heating chamber4 so as to be in a suitable position above the tops and out of the wayof the cupels, which are not shown in the .drawing. This heating element38 may be made of any suitable material and is shown constructed ofzig-Zag shape with a centre space or gap This form of resistance orelement is best adapted to effect a practically uniform distribution ofthe heat throughout the heating'chamber 4:,and the gap or space 39prevents excessive heating of the element whichwould otherwise obtain atthis point. The element 38 is supported at suitable points by hook bolts40, of refractory material, from the top or roof of the box or part 1.The leads 41 for the element 38 pass through holes or openings 42 in theback of the boxes or parts 1 and 8 and slab 28 to the exterior of themuffle, and are suitably connected to the electrical wires or conductors43 by'suitable terminals. The leads or portions 41 which pass throughthe openings 42 and connect the element 38 with the electrical wires I3are of considerably greater cross-sectional area than the element 38,so" that little or no heat is generated in said leads 41.

In the modification illustrated in Fig. 4, the roof or upper portion ofthe box or part 1, which provides the heating chamber at, is arched orcurved, andthe roof or upper portion of the box orpart 8 is similarlyarched or curved. In this way the upper portion of the space or chamber9 is of arch shape. In this modification the heating element 38 willalso be arched or curved. In other respects the muffle or muffle furnacemay be similar to that described, andshown in Figs. 1 to'3.

What I claim as my invention and desire to protect by Letters Patent is1- 1. A muffle, muffle furnace or the like, comprising an inner partwhich provides the heating chamber, an outer casing enclosing said innerpart and forming 'a'space between it and said inner part, said outercasing being provided with an inlet for air leading into said space, andthe inner part being constructedwith a row of holes along each side nearthe floor which allow air which is preheated in its passage through theinlet and space to pass directly into the heating chamber, electricalheating means in said heating chamber, and an outlet leading from theheating chamber to the open, as set forth.

2. A muille, muiile furnace or the like comprising an inner part whichprovides the heating chamber, an outer casing enclosing said inner partand forming aspace between it and said inner part, said outer casingbeing provided with an inlet for air leading into said space, and theinner part being'constructed with a row of holes along each side nearthe floor, a slab arranged at the front end of the inner part, whichcloses the space between said inner part and the outer casing at thefront and is provided with a plurality of holes which lead from'thespace to the front of the heatingchamber, said holes in the inner partand slab allow-ing'air which is preheated in its passage through theinlet and spaceto pass into the heating chamber,

electrical heating means in said heating chamber, and an outlet leadingfrom the heating chamber to the open, as set forth.

3. A mufiie, muffle furnace or the like, comprising an inner part whichprovides the heating chamber, an outer casing enclosing said inner partand forming a space between it and said inner part, said outer casingbeing provided with an inlet for air leading into said space, and theinne part being constructed with a row of holes along each side near thefloor which allow air which is preheated in its passage through theinlet and space to pass directly into the heating chamber, electricalheating means, in the form of an element or resistance of zig-zag shapeconstructed to forma gap at the center thereof, in said heating chamber,and an outlet leading from the heating chamber to the open, as setforth.

4. A muffle, muffle furnace or the like, comprising an inner part whichprovides the heating chamber, an outer casing enclosing said inner partand forming a space between it and said inner part, said outer casingbeing provided with an inlet for air leading into said space, and theinner part being constructed with a row of holes along each side nearthe floor which allow air which is preheated in its passage through theinlet and space to pass into the heating chamber, electrical heatingmeans, in the form of an element or resistance of zig-zag shapeconstructed to form a gap at the centre thereof, in said heatingchamber, means for suspending the element from the top of the heatingchamber comprising hook-shaped members of refractory material, and anoutlet leading from the heating chamber to the open, as set forth.

5. A muffle, muffle furnace or the like, comprising an inner part whichprovides the heating chamber, an outer casing enclosing said inner partand forming a space between it and said inner part, said outer casingbeing provided with an inlet for air leading into said space, and theinner part being constructed with openings which allow air which ispreheated in its passage through the inlet and space to pass into theheating chamber, electrical heating means in said heating chamber, anoutlet leading from the heating chamber to the open, and meansco-operating with said outlet for inducing a current of air through themuffle furnace, as set forth.

6. A muffle, muffle furnace or the like, comprising an inner part whichprovides the heating chamber, an outer casing enclosing said inner partand forming a space between it and said inner part, said outer casingbeing provided with an inlet for air leading into said space, and theinner part being constructed with openings which allow air which ispreheated in its passage through the inlet and space to pass into theheating chamber, electrical heating means in said heating chamber, anoutlet leading from the heating chamber to the open, and meanscooperating with said outlet for inducing a current of air through themuffle furnace, said latter means consisting of a nozzle for directing ajet of compressed air, as set forth.

7. A muffle, muflie furnace or the like, comprising an inner part whichprovides the heating chamber, an outer casing enclosing said inner partand forming a space between it and said inner part, said outer casingbeing provided with an inlet for air leading into said space, and theinner part being constructed with openings which allow air which ispreheated in its passage through the inlet and space to pass into theheating chamber, electrical heating means in said heating chamber, anoutlet leading from the heating chamber to the open, a fluecommunicating with the outlet, and a nozzle directing a jet ofcompressed air through the flue for inducing a current of air throughthe muffle or furnace, as set forth.

8. A muffle, mufile furnace or the like, comprising an inner part, ofarch shape in its upper portion, which part provides the heatingchamber, an outer casing of arch shape in its upper portion, whichcasing encloses said inner part and forms a. space between it and saidinner part, said outer casing being provided with an inlet for airleading into said space, and the inner part being constructed with a rowof holes along each side near the floor which allow air which ispreheated in its passage through the inlet and space to pass directlyinto the heating chamber, electrical heating means of arch shape in saidheating chamber, and an outlet leading from the heating chamber to theopen, as set forth.

In testimony whereof I have signed my name to this specification.

PHILIP HENRY PARR MONCKTON.

